Fluid pump

ABSTRACT

A DISPLACEMENT ELEMENT FOR A FLUID PUMP COMPRISED OF OPPOSED, CONNECTED MEMBERS OF A MEMORY HEAT TREATABLE MATERIAL SUCH AS 55-NITINOL WITH AN ELECTRICAL CONTROL CIRCUIT USED TO ALTERNATELY CAUSE EACH OF THE MEMBERS TO ASSUME ITS MEMORY HEAT TREATED CONFIGURATION, THEREBY CAUSING CYCLICAL MOVEMENT OF THE MEMBERS. THIS MOVEMENT IS UTILIZED TO CREATE THE PUMPING ACTION BY EMBEDDING THESE ELEMENTS IN A DIAPHRAGM ELEMENT TO CREATE A DIAPHRAGM PUMP.

sept. 20, 1971 J, P, MADURSK| ETAL 3,606,592

FLUID PUMP Filed may 2o, 1970 LL .VI Jrlfl United Smm Patent Ot3,606,592 Patented Sept. 2o, 1971 3,606,592 FLUID PUMP Joseph P.Madurski and Ambrose Tomala, Royal Oak, Mich., assignors to The BendixCorporation Filed May 20, 1970, Ser. No. 39,952 Int. Cl. F04b 19/02,43/02 U.S. Cl. 417-413 6 Claims ABSTRACT OF THE DISCLOSURE Adisplacement element for a fluid pump comprised of opposed, connectedmembers of a memory heat treatable material such as 55-Nitinol `with anelectrical control clrcuit used to alternately cause each of the membersto assume its memory heat treated configuration, thereby causingcyclical movement of the members. This movement is utilized to createthe pumping action by embedding these elements in a diaphragm element tocreate a diaphragm pump.

BACKGROUND OF THE INVENTION The great need for a practical artificialheart and the resulting widespread research and development effortsexpended towards providing for this need has made clear the specialdesign requirements necessary in order for any such device to besuccessful.

These requirements include compactness, simplicity, reliability, and theability to operate efficiently on a minimum power input.

In providing these requirements, it would be desirable to have a directand efficient conversion of electrical or thermal energy to mechanicalenergy with a minimum of mechanical parts. Prior art pumps have includedthose having piezoelectric diaphragms, in which a piezoelectric ceramicmaterial such as barium titanate is alternately pulsed to provide adirect mechanical output. While satisfactory for some applications,these devices suffer from the drawback of relatively low displacementsof the piezoelectric material, leading to high power consumption, poorefficiencies, and complexity of design in the power circuit and valving,hence rendering such devices unsatisfactory for artificial heart orcardiac assist applications.

Hence, it is an object of the present invention to provide adisplaceable element arrangement for pump applications which directlyconverts electrical or thermal energy into a mechanical output with aminimum number of parts.

SUMMARY OF THE INVENTION This object and others which will becomeapparent upon a reading of the following specification and claims areaccomplished by providing a pumping member including a pair ofinterconnected members of a memory heat treatable material such as55-Nitinol, heat treated in opposed configurations so that causing thesemembers to alternately assume their heat treated configuration willprovide a cyclical displacement of the pumping member.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. ll is a sectional view of a pumputilizing the pumping member according to the present invention.

FIG. 2 is a front elevation of the pumping member shown in FIG. 1,together with a schematic representation of the electrical controlcircuit.

FIG. 3 is a view of the section created by cutting plane 3-3 in FIG. 2.

FIG. 4 is a sectional view of a double acting pump incorporating apumping member according to the present invention.

DETAILED DESCRIPTION In the following detailed description, certainspecific terminology will be employed for the sake of clarity and aspecific embodiment and application will be described in order toprovide a complete understanding of the invention, but it is to beunderstood that the invention is not so limited, and may be practiced ina variety of forms and embodiments.

Referring to the drawings, and particularly FIG. 1, a diaphragm typepump 10 is shown utilizing a displacement element pumping memberaccording to the present invention as the diaphragm 12. The diaphragm 12is secured between housing members 14, 16 to divide the space formed bythe members 14, 16 into a pair of chambers 18, 20. Movement of thediaphragm 12 to increase the volume of chamber 18 draws fluid into theinlet 22 via check valve 24. Fluid is prevented from reentering thechamber 18 from the outlet 26 by means of the check valve 28.

Movement of the diaphragm 12 so as to reduce the Volume of the chamber18 causes fluid contained therein to be advanced through the outlet 26via check valve 28, being prevented from backing out the inlet 22 by theaction of the check valve 24.

As shown in FIGS. 2 and 3, the diaphragm 12 is comprised of a flexiblerubber or plastic body 30 having embedded therein grids 32, 34 of wireor strip elements extending transversely to each other.

The material of which these grids are formed is of a material having aheat treat memory, such as 55-Nitinol.

55-Nitinol is the generic name given to a group of alloys having 53-57percent nickel with the remainder titanium.

This material has the characteristic above referred to: a mechanicalheat treat memory.

SS-Nitinol, if constrained to have a particular shape while heat treatedabove a certain temperature (approximately 900 F.) will return to thisconfiguration with considerable force, even if being plasticallydeformed in the interim, upon being heated to a certain temperaturewhich may vary, depending on the composition of the alloy from -60 F. to+300 F.

The straining to an intermediate shape differing from the memory heattreat shape, giving the restorative heat treat (RHT), and cooling toambient temperatures is referred to as the yStrain-Heat-Cool cycle (SHC)and may be repeated over and over on the order of millions of cycles,which is the basic mechanism relied on in the present invention.

The precise behavioral characteristics of the displacement members willvary with the composition, temperature, and percent of strain, and inproviding an actual design, all of these factors must be considered inarriving at the specific performance characteristic desired.

These characteristics have been established to a considerable extent anddetails thereof are contained in numerous patents and applicationsincluding the following U.S. patents: 3,174,851 (basic composition ofmatter patent), 3,351,463; 3,352,650; 3,352,722; 3,391,882; 3,403,238;3,416,342. Publications include Materials and Processes for the 70s,Investigations of the Unique Memory Properties of 55-Nitinol Alloy,Proceedings of the 15 National SAMPE Symposium and Exhibition, Apr.29-May 1, 1969, pp. 265-274; A Summary of Recent Research on the NitinolAlloys and Their Potential Application in Ocean Engineering, OceanEngineering, l, -120 (1968).

Inasmuch as the details of these characteristics do not in themselvesform a part of the present invention and are Well known and available tothe public as indicated by the above references, it is not feltnecessary to include data on these in detail.

The grids 32, 34 are given memory heat treats so as to have opposingconfigurations. That is, in the position shown in FIG. 3, one of thegrids is in its memory heat treat configuration while the other isdeformed out of its memory heat treat configuration, while conversely,in the diaphragm position shown in phantom in FIG. 3, the other of thegrids is in its memory heat treat configuration while the one grid isdeformed out of its memory heat treat configuration.

As shown schematically in FIG. 2, a power suppy unit 36 is shown, whichalternately and successively supplies electrical power to the grids 32and 34. This electrical power is selected to be of a sufiicient level tocause the grid supplied to be raised to or above its RHT temperature,thus causing the grid supplied to assume its memory heat treatconfiguration.

If the grid so supplied is in a deformed condition at the moment itreaches its RHT temperature, it will snap back with considerable force.This action has a two-fold effect: movement of the diaphragm causes thepumping action to take place; and the other grid by means of the drivingconnection therebetween formed by the rubber sheet 30 is deformed out ofits MHT configuration. Upon the application of the electrical energy tothe grid so deformed, the diaphragm will then snap back to its originalposition, while deforming again the other grid which has then cooledbelow its RHT temperature and so on.

The movement of the fiuid through the unit will tend to prevent thetemperature of the grids from building up beyond their respective RHTtemperatures. This RHT temperature is selected to be well above ambientconditions so that the electrical energy must be applied in order tocause the respective grids to assume their MHT configurations.

The grid sizes, the power levels, and frequency of the pulses, theinsulating needs between the grids and the other specific details ofdesign will vary with the particular composition of the grid material,the operating temperature involved, the performance characteristicsrequired, the fluid to be pumped, the mechanical strain induced by thediaphragms movement, the properties of the diaphragm sheet 30, and anumber of other factors. Hence, in arriving at a specific design, all ofthese factors must be considered, and by applying general engineeringprinciples, their effect on the design characteristics may be foreseenand a desired performance provided.

This basic arrangement may be extended to a great number of other pumpconfigurations and installations as shown in FIG. 4, which illustrates adouble acting pump, which advances fiuid from a second inlet 40 to asecond outlet 42 on the back stroke of the diaphragm.

Of course, in-line, circulating, ganged, etc., pump installations in avariety of environments are possible in this same context.

Similarly, the particular configuration of the opposed members 32, 34may be varied as required, as leaf, strip or other forms are well withinthe scope of the present invention.

In this same context, other applications of the opposed member mechanismare possible in which the large displacement, direct energy conversioncharacteristic may be used to advantage.

From the above description, it can be appreciated that an extremelysimple, effective, and reliable displacement device suitable forartificial heart and cardiac assist device applications has beenprovided, without the need for complex mechanisms.

What is claimed is:

1. A fiuid pump comprising:

a housing member defining a pumping chamber;

a displacement element disposed in said chamber including a first memberhaving a memory configuration to which it may be controllably restored;a second member having a memory configuration to which it may becontrollably restored; means drivingly connecting said first and secondmembers so that when either of said elements is in its memoryconfiguration the other is distorted out of its memory configuration,control means alternately causing said first and second members to tendto assume their memory configurations to cause said displacement elementto alternately move to a position corresponding to each of said membersmemory configurations;

means for creating a pumping action through said chamber in response tosaid movement of said displacement element, whereby a pumping action maybe created by said control means.

2. The pump of claim 1 wherein said first and second members are of amemory heat treatable material and wherein each of said control meansrestores said memory configurations by heating each of said members toits restorative temperature.

3. The pump of claim 2 further including a plurality of each of suchfirst and second members and wherein said means drivingly connectingsaid plurality of first and second members includes a diaphragm memberand means embedding said plurality of first and second members in saiddiaphragm member.

4. The pump of claim 3 wherein said plurality of first and secondmembers extend transversely to each other.

5. The pump of claim 2 wherein said first and second members arecomposed of -Nitinol.

`6. The pump of claim 2 wherein said first and second members arecomposed of an alloy having 53-57 percent by weight of nickel with theremainder titanium.

References Cited UNITED STATES PATENTS 2,630,760 3/1953 Ryba 417-4133,516,082 6/1970 Cooper S40-227.1

ROBERT M. WALKER, Primary Examiner U.S. Cl. X.R. 92--103

